Viruses and Bacteria

What do you understand Viruses and Bacteria mean?

The statistics are astounding! A recent study revealed that nearly one out of four college women tested in Seattle, Washington arc harboring a sexually transmitted virus that is strongly associated with cancer of the cervix. Computer color enhanced, these deadly virus particles are shown in the photo, as the green spheres speckled with red. The human cell they are destroying is yellow.

The human papillomavirus (HPV) causes a sexually transmitted disease commonly known as genital warts. HPV comes in 60 different varieties. Infection with any one of the 60 types can lead to an outbreak of warts, although some are more likely to cause warts than others. Ironically, the types that most often result in warts are the least dangerous. HPV types such as HPV 16 rarely cause warts on infection but are those most likely to be associated with cancer and the least likely to be detected. Two other viral diseases transmitted by sexual contact arc genital herpes and AIDS. Unlike sexually transmitted diseases (STDs) spread by bacteria, viral STDs cannot be cured. The drugs available to treat these diseases only help ease the symptoms but cannot destroy the viruses. Why are these diseases different in that regard? What makes a virus so hard to kill?

 What is Viruses?

Viruses are infectious agents. They enter living organisms and cause disease. But although viruses invade living things and cause cells to make more viruses, the viruses themselves are not living! They do not have a cellular structure, which is the basis of all life. They are nonliving obligate parasites, which means that viruses cannot reproduce outside of a living system. They must exist in association with and at the expense of other organisms. Unfortunately, that "other organism" may be you!
 

How does the viruses discovered by human?

At the end of the nineteenth century, several groups of European scientists working independently first realized that viruses existed. As they filtered fluids derived from plants with tobacco mosaic disease and cattle with hoof-and-mouth disease, the scientists discovered that the infectious agents passed right through the fine pored filters they used, which were designed to hold back bacteria. They concluded that the infectious agents associated with these diseases were not bacteria they were too small. As they studied the filtrate containing these mysterious agents, the scientists also discovered that the disease-causing agents could multiply only within living cells. These infection agents, they hypothesized, must lack some of the critical "machinery" cells use to reproduce. For many years after their discovery, viruses were regarded as very primitive.forms of life, perhaps the ancestors of bacteria. Today, scientists know that this view is incorrect—viruses are not living organisms. The true nature of es became evident in the 1930s after the ground-break-g work of an American scientist, Wendell Stanley. Stanley pared an extract of tobacco mosaic virus (TMV), purified and studied its chemical composition. His conclusion: V was a protein—and he was partially right. Scientists later discovered that TMV also contains ribonucleic acid, or A. In the late 1930s, with the development of the electron microscope, scientists were able to see the virus that Stanley purified.

What is the structure of Viruses?

Viruses primarily infect plants, animals, and bacteria. A specific virus can only infect a certain species of organisms. So you cannot be infected by a bacterial virus, nor can your dog catch your cold. Some viruses, however, can infect more than a single species of organism; for example, the human immunodeficiency virus (HIV virus that causes acquired immunodeficiency syndrome [AIDS]) is thought to have been introduced to humans from African monkeys. Each virus has its own unique shape (pic), but all contain the same basic parts: a nucleic acid core (either DNA or RNA) and a protein "overcoat" called a capsid. The structure of the TMV is shown in pic, B and illustrates one way that a virus is put together. This virus is helical, with its single strand of RNA coiled like a spring, surrounded by a spiraling capsid of protein molecule,i. Many viruses have another chemical layer over the capsid called the envelope, which is rich in proteins, lipids, and carbohydrate molecules. pic,A is an electron micrograph of a typical enveloped virus, the causative agent of herpes. Its structure is in near picture.